Vent and destruct system

ABSTRACT

A vent and destruct system for balloons and the like which utilizes pyrotechnic strands covered with tubes of braided copper wire to perform the functions of venting and destructing. The braided copper wire covering on the pyrotechnic strands provides a safety means by preventing static electricity from accidentally igniting the pyrotechnic strands when the system is being attached to a balloon or the like. When the system is activated the tubes of braided copper wire are destroyed by the heat produced by the pyrotechnic strands.

United States Patent Rentz et al.

[451 May 22,1973

VENT AND DESTRUCT SYSTEM Inventors: Albert W. Rentz; Lloyd J. Jackson;

Robert C. Willard; Vernon D. Burklund, all of China Lake, Calif.

The United States of America as represented by the Secretary of the Navy, Washington, DC.

Filed: Sept. 29, 1971 Appl. No.: 184,966

Assignee:

US. Cl. ..102/27 R, 102/70 R int. Cl ..C06c 5/06 Field of Search ..102/27, 70

References Cited UNITED STATES PATENTS 3/1931 Fritzsche .102/27 R 3,129,663 4/1964 Schnepfe, Jr. ..102/27 R 3,382,802 5/1968 Prior et al. ..102/27 R 3,661,087 5/1972 Willard et al. ..102/27 R Primary ExaminerVerlin R. Pendegrass Att0rney- R. S. Sciascia, Roy Miller and Lloyd E. K. Pohl [5 7 ABSTRACT A vent and destruct system for balloons and the like which utilizes pyrotechnic strands covered with tubes of braided copper wire to perform the functions of venting and destructing. The braided copper wire covering on the pyrotechnic strands provides a safety means by preventing static electricity from accidentally igniting the pyrotechnic strands when the system is being attached to a balloon or the like When the system is activated the tubes of braided copper wire are destroyed by the heat produced by the pyrotechnic strands.

3 Claims, 2 Drawing Figures PATENTEL MY 3? 3 FIG.

9P 0 z w 1 M 5 m 2 m5 Mu FIG. 2.

VENT AND DESTRUCT SYSTEM BACKGROUND OF THE INVENTION l. Field of the Invention This invention relates to vent and destruct systems for balloons and the like. More particularly, this invention relates to vent and destruct systems for balloons and the like which utilize burning strands of pyrotechnic material to slit the material of the balloon.

2. Description of the Prior Art Balloons are commonly used to hoist and suspend flares. When a balloon is used for this purpose it is desirable to have the balloon hoist the flare to some predetermined height and then retain the flare at that height until the flare burns itself out. Some balloons have a tendency to rise as the weight of the flare decreases and it is necessary to cause some of the gas to escape to reduce lift. Also, once the flare has burned itself out, it is desirable to have the balloon collapse and fall to earth along with the burned out flare. To assist in accomplishing these functions, systems called vent and destruct systems have been devised.

One type of vent and destruct system relies essentially on a covered slow burning fuse, two lengths of bare pyrotechnic material, and a firing mechanism to perform its functions. The firing mechanism is attached to one end of the covered slow burning fuse, a short length of pyrotechnic strand to an intermediate point on the slow burning fuse, and a long length of pyrotechnic strand to the other end of the fuse. After assembly, the system is affixed to the surface of a balloon, usually by means of pockets sewn on the balloon, in a manner whereby the firing mechanism will ignite the covered slow burning fuse when the balloon is deployed. As the balloon is deployed the firing mechanism ignites the slow burning fuse. While the balloon is in flight, the covered slow burning fuse burns and eventually ignites the short length of pyrotechnic strand intermediate between its ends. Since the pyrotechnic strand is bare and has its burning surface in direct contact with the balloon surface, it quickly burns a slit in the balloon. Since the first pyrotechnic strand is short, it burns only a short slit in the balloon which acts as a vent, permitting some of the gas to escape from the balloon and causing the balloon to stop rising and remain stationary in the air with respect to altitude. After the covered slow burning fuse has ignited the first pyrotechnic strand it continues to burn until its flame reaches and ignites the long length of pyrotechnic strand. The long length of pyrotechnic strand burns a long slit in the balloon, allows all of the remaining gas to escape and completely destructs the balloon. Thus, the system is called a vent and destruct system.

In vent and destruct systems of the type described above, the slow burning fuse is generally fabricated from a slow burning material of the type used to fabricate articles such as dynamite fuses. Such a material is relatively safe to work with in that it is not likely to be ignited accidentally. Furthermore, the slow burning fuse is covered, except for gaps to permit contact with the fast burning pyrotechnic strands, with some material to prevent it from being in direct contact with the material of the balloon surface while it is burning.

On the other hand, the pyrotechnic strands are commonly fabricated from an extremely inflammable material such as magnesium-Teflon and such a material can be ignited by only a spark of static electricity. Since,

balloons are commonly fabricated from or contain nylon and nylon is well known to spark easily when rubbed with a conductive material it may be seen that the insertion of bare pyrotechnic strands into pockets sewn on the surface of a balloon is an extremely hazardous occupation.

SUMMARY OF THE INVENTION It has now been found that magnesium-Teflon pyrotechnic strands are safe to handle when covered with tubes of braided copper wire and that the braided tubes do not deleteriously affect the ability of the pyrotechnic strands to vent and destruct balloons and the like. Thus, the present invention represents an improvement over the prior art in that it is completely safe to handle.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view of a balloon vent and destruct system; and

FIG. 2 is a cross sectional view of branching site 15 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT A balloon vent and destruct system according to this invention is improved over those described in the prior art in that the pyrotechnic strands, as well as the slow burning fuse, are covered. The covering utilized is braided copper wire in the form of a tube.

FIG. 1 is an elevational view of the system. The system comprises an igniter 11, two lengths of slow burning fuse l2 and 12' encased in tubes of braided copper wire, a venting pyrotechnic strand 13 encased in a tube of braided copper wire, and a destroy pyrotechnic strand 14 encased in a tube of braided copper wire. A flared copper tube is utilized to affix the venting pyrotechnic strand at branching site 15 and a copper tube is utilized to affix the destroy pyrotechnic strand to the slow burning fuse at branching site 16 in a similar manner.

FIG. 2 is a cross sectional view of branching site 15. The branching site is a place where the first length of slow burning fuse 12, the second length of slow burning fuse 12 and the venting pryotechnic strand 13 are held in close proximity to one another so that the first length of slow burning fuse can cause the second length of slow burning fuse and the venting pyrotechnic strand to be ignited. The venting pyrotechnic strand is encased in a tube of braided copper wire 23, the second length of slow burning fuse is encased in a tube of braided copper wire 24 and both are crimped into the flared end of a flared copper tube 17. The pyrotechnic strand actually consists of a tube of magnesium-Teflon 22 with a paladium-aluminum Pyrofuze 19 inserted a few inches into the end of it. Pyrofuze extends from the end of the strand and is folded over the end of slow burning fuse 12 as depicted in order to insure easy and complete ignition of the fuse. A short length of polyolefin shrink tubing 26 is placed around the end of the pyrotechnic strand to prevent the strand from being broken or damaged or slipping as it is crimped into the flared copper tube. In addition to preventing damage or slipping, the polyolefin shrink tubing 26 protects the paladium-aluminum Pyrofuze within the strand from being excessively dented inwardly as the flared copper tube is crimped on the strand. This prevention of inward denting assists in preventing failure of the Pyrofuze.

The small end of the flared copper tube 17 is crimped on to the end of the first length of slow burning fuze 12. The first length of slow burning fuse has an ignition pellet 20 which is fabricated from thermite or the like attached to it. The pellet is held in place by means of a cup 21 crimped on to the end of the fuse. The cup is fabricated from any material which can be easily melted such as mild steel or plastic. The braided copper wire tube 25, which covers the first length of slow buming fuse, is stretched over the flared copper tube as depicted. The inside diameter of one end of a tube of braided copper wire can be greatly enlarged by grasping that end and pushing it toward the other end. Thus, the tube of braided copper wire 25 is initially cut so that it will extend somewhat beyond the end of the slow burning fuse and the free end is enlarged and stretched over the copper tube. A tube of polyolefin shrink tubing 18 covers the entire branching site and completes the site.

Branching site 16 is similar to branching site except that only a pyrotechnic strand extends from the site and a non-flared copper tube is used to crimp the pyrotechnic strand l4 and slow burning fuse 12 in close proximity to one another.

A completely covered vent and destruct system according to this invention is attached to a balloon or the like and operates in a manner similar to prior art systems which utilize bare pyrotechnic strands. That is, the firing mechanism is used to ignite the first length of slow burning fuse as the balloon is released, the first length of slow burning fuse eventually ignites the second length of slow burning fuse and the venting pyrotechnic strand and the second length of slow burning fuse eventually ignites the destruct pyrotechnic strand. The lengths of the various fuses and strands and their burning rates determine the timing of the operation.

In tests conducted with 1700 braided copper wire covered systems and 1700 balloons, not one accidental injury was sustained due to premature ignition of the pyrotechnic strands. Furthermore, the completely covered pyrotechnic strands performed the functions of venting and destructing with facility equal to or surpassing that of bare pyrotechnic strands even though they were covered. That is, magnesium-Teflon strands and the like were found to produce temperatures of sufficient magnitude to destroy the braided copper wire covering and still burn slits in the balloon surface.

While FIG. 2 shows one way in which the venting pyrotechnic strand can be attached to the system, it should be realized that there are many other possible ways. For example, a copper tube in the form of a T may be used in lieu of the flared copper tube of FIG. 2. And one length of slow burning fuse may be used in lieu of the two lengths described above. There are a number of ways, which will be readily apparent, of affixing a venting pyrotechnic strand to a system utilizing one length of slow burning fuse in a manner whereby the venting pyrotechnic strand will be ignited as the slow burning fuse burns past.

What is claimed is:

l. A vent and destruct system for balloons comprising:

a. a firing mechanism;

b. slow burning fuse means affixed to the firing mechanism in a manner whereby said slow burning fuse means will be ignited by said firing mechanism when the mechanism is fired;

c. a venting pyrotechnic strand affixed to the system at a point intermediate between the ends of the slow burning fuse means in a manner whereby it will be ignited as the slow burning fuse means burns y;

d. a destruct pyrotechnic strand affixed to the slow burning fuse means at the end of said means most remote from the firing mechanism in a manner whereby it will be ignited by said means as said means finishes burning; and

e. tubes of braided copper wire completely covering all exposed parts of said slow burning fuse means and said pyrotechnic strands.

2. A vent and destruct mechanism according to claim 1 wherein said slow burning fuse means consists of two lengths of slow burning fuse, the second length of which is ignited by the first length as the first finishes burning and wherein the venting pyrotechnic strand is attached to the system in a manner whereby it is ignited at the time when the first length of slow burning fuse finishes burning.

3. A vent and destruct system according to claim 2 wherein the ends of said second length of slow burning fuse and said venting pyrotechnic strand are affixed in close proximity with the end of said first length of slow burning fuse by means of a crimped on flared copper tube. 

1. A vent and destruct system for balloons comprising: a. a firing mechanism; b. slow burning fuse means affixed to the firing mechanism in a manner whereby said slow burning fuse means will be ignited by said firing mechanism when the mechanism is fired; c. a venting pyrotechnic strand affixed to the system at a point intermediate between the ends of the slow burning fuse means in a manner whereby it will be ignited as the slow burning fuse means burns by; d. a destruct pyrotechnic strand affixed to the slow burning fuse means at the end of said means most remote from the firing mechanism in a manner whereby it will be ignited by said means as said means finishes burning; and e. tubes of braided copper wire completely covering all exposed parts of said slow burning fuse means and said pyrotechnic strands.
 2. A venT and destruct mechanism according to claim 1 wherein said slow burning fuse means consists of two lengths of slow burning fuse, the second length of which is ignited by the first length as the first finishes burning and wherein the venting pyrotechnic strand is attached to the system in a manner whereby it is ignited at the time when the first length of slow burning fuse finishes burning.
 3. A vent and destruct system according to claim 2 wherein the ends of said second length of slow burning fuse and said venting pyrotechnic strand are affixed in close proximity with the end of said first length of slow burning fuse by means of a crimped on flared copper tube. 